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Comment

If I may, would like to offer 2.5mm is not large enough 3 to 3.5 will stop the surface tension. Or you can make your vents oval in shape. In the US I use a 1/8 inch drill bit (something like 3.1mm).
slow getting back to water line sounds more like water is getting trapped and slowly draining out,relieving the extra weight bringing your sub to waterline. Are there areas in the freeboard or sail that may need some drainage passageways?

If you can cut, drill, saw, hit things and swear a lot, you're well on the way to building a working model sub.

Comment

Rob, my type VII has the same issue, when you make a static dive and re-surface, water will stick underneath your deck, giving you a wet deck, this will add weight, after some time the water will find it's way restoring you to your waterline, that's normal with this type of boats.
As you stated diving dynamic you don't have this problem, it's the same with mine, movement speeds up the proces in removing the water from your deck, it will be interesting to see if using the PAM can solve that problem.

Comment

That's very reassuring, I think the complex hull shape doesn't help either, def getting air trapped at the top of the saddle tanks, but I can't drill any more holes or it will look terrible.

I wondered would the very thin openings on the deck be an issue, but glad it's an issue with Type VIIs and not my build.

Rob

About those thin slits in the deck. When dry (the first dive of the session) they are all open and vent the hull quickly and thoroughly. However, when you surface, water tension blocks those little slits with water, inhibiting the next attempt to dive, unless you give the deck time to dry out. When wet, the deck just won't vent properly. Hello, Pam.

David

"... well, that takes care of Jorgenson's theory!"

Comment

Reminds me when I built the 1/96 scale model of Trutta SSN 421. The slits were about the same. Dive the boat and watch the bubbles race around under the deck , just couldnít break surface tension. She would surface with a pronounced list port or Starboard randomly. I solved it with some hidden but unscale 1/8 inch holes fore and aft , and along the deck edge. I think on this Type VII One could hide, a couple good holes under the net cutter supports, open up the bullnose , hide a couple under the wire guide supports aft, oh and yes, our good friend Pam. Itís not the Type VII in particular that exihibits this problem. All early submarines with those big flat decks do this. I think itís one reason why the stock Robbe deck had such outrageously out of scale deck openings.

Comment

The remark about the slits is right, hope that using pam will solve that.
I'm not sure but, it would not surprice me, that my teacher( from which the boat originally was) counted in the wet deck when trimming it on the waterline, those boats where on the waterline when fully loaded and ran much higher when unloaded, maybe you can trim her such way.
As for airblubbles, the towingtube at the bow is opened up and i've got me some actual ventholes at the stern.

Manfred.

Fertig zum unterwasser.

Comment

As I start the paint job, I've taken those tips on board, I've had to add some extra vents on the saddle tanks, just too much air was trapped below. Not prototypical, but it's a trade off between scale and not effing working properly.............practicality won in the end!

The sub gets a coat of Halfords primer from a rattle can, I'm using a slightly heavy paint for the first coat which will be sanded back and subsequent ones will be a lighter primer..........

.............plus intermediate steps of filling and sanding the blemishes, mostly the seams are an issue......

........but it is a massive relief after almost two years to see a uniform colour, all the odd shapes and colours have blended. With the hull sections I expect to paint/fill/sand/repaint around four times, I should have all the blemishes sorted by that stage.

The additional parts get a coat of primer also.

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On the downside I broke the scratchbuilt 2.2mm deck gun at a point that can't be re-soldered, so ordered the 1/35 kit from Accurate Armour, will use the best of boat guns for version 2.